The present invention pertains to a digital image compressing and recording apparatus. In particular, the present invention relates to a multiple channel image compressing and recording apparatus and its method for compressing and recording digital images for multiple channels.
As well known, in the case of recording an image used for the purpose of monitoring using a camera or the like, in general, it is required to record images over a long period of time. Thus, this recording requires a recording medium with its large capacity.
However, an image used in the case of such monitoring does not always need to be continuously recorded, and is often recorded intermittently for a need for reducing a recording capacity. Such recording is often called as time lapse recording.
For the purpose of monitoring or the like, there is many cases in which there are a plurality of monitoring sites. In such a case, a plurality of monitoring sites are intermittently monitored sequentially, and the intermittent images of multiple channels are transmitted or recorded.
On the other hand, with advancement of digital technology in recent years, an image is digitally processed. However, in order to obtain a digital image, it is required to record a large amount of information.
Therefore, in order to reduce an amount of information, there have been rapidly popular image compression techniques such as JPEG (Joint Photographic Experts Group) or MPEG (Moving Picture Image Coding Experts Group) for compressing an image utilizing image redundancy.
Thus, time lapse recording at a plurality of sites is performed by using digital technology, whereby an image can be compressed by utilizing image redundancy. In this case, as image compressing means, there is known time lapse recording using JPEG.
However, JPEG is a compression system disadvantageous in that the compression rate is not so high.
On the other hand, a correlation between frames can be obtained by using the MPEG technique. However, in the case of multiple channels, images before and after channel to be switched is an image at another monitoring site, and it is general that there is no correlation between images. Thus, there occurs inconvenience that, even if a correlation between frames is obtained, image compression is not made.
Because of this, the Applicant files an application for an image compressing apparatus comprising an image buffer memory for each channel, wherein a correlation between frames is obtained for each channel, whereby compressing and encoding such as MPEG can be performed (Japanese Patent Application No. 11-276922).
It is an object of the present invention to provide a multiple channel image compressing and recording apparatus and method therefor capable of displaying a site in detail for a predetermined time even if an attempt is made to strengthen monitoring midway without degrading an image quality even if intermittent recording is performed over a very long time.
A multiple channel image compressing and recording apparatus according to the present invention comprises: an intermittently recording section for intermittently recording digital images of plurality of inputted channels in a memory in units of frames; a first compressing and recording section for performing compressing and encoding by obtaining a correlation between frames for each channel relevant to a digital image intermittently recorded in a memory in units of frames by this intermittent recording section while a time interval of intermittent recording is shorter than a predetermined value, and then, causing recording in a recording medium; and a second compressing and recording section for performing compressing and encoding in a frame relevant to digital images of multiple channels, and then, causing recording in a recording medium.
In addition, the multiple channel image compressing and recording apparatus according to the present invention comprises: a memory causing the inputted digital image of multiple channels to be intermittently recorded, respectively, for each channel in units of frames; a first compressing section for performing compressing and encoding by obtaining a correlation between frames for each channel relevant to the digital images intermittently recorded in this memory in units of frames; a second compressing section for performing compressing and encoding in a frame relevant to the digital images of multiple channels; and a recording section for recording an output of the first compressing section while a time interval of intermittent recording relevant to a memory is shorter than a predetermined value, and then, recording an output of the second compressing section while a time interval of intermittent recording exceeds a predetermined value.
Further, the multiple channel image compressing and recording method according to the present invention comprises: an intermittent recording step of intermittently recording the inputted digital images of multiple channels in a memory for each channel in units of frames; a first compressing and recording step of performing compressing and encoding by obtaining a correlation between frames for each channel relevant to the digital images intermittently recorded in a memory in units of frames by this intermittent recording step while a time interval of intermittent recording is shorter than a predetermined value, and then, causing recording in a recording medium; and a second compressing and recording step of performing compressing and encoding in a frame relevant to the digital images of multiple channels while a time interval of intermittent recording exceeds a predetermined value, and then, causing recording in a recording medium.
Furthermore, the multiple channel image compressing and recording method according to the present invention comprises: an intermittent recording step of intermittently recording inputted digital images of multiple channels in a memory in units of frames for each channel, respectively; a first compressing step of performing compressing and encoding by obtaining a correlation between frames for each channel relevant to the digital image intermittently recorded in a memory in units of frames by this intermittent recording step; a second compressing step of performing compressing and encoding in a frame relevant to the digital images of multiple channels; and a recording step of recording an output of the first compressing step while a time internal of intermittent recording relevant to a memory is shorter than a predetermined value, and then, recording an output of the second compressing step in a recording medium while a time interval of intermittent recording exceeds a predetermined value.
With the above arrangement and method, in general, compressing and encoding utilizing a correlation between frames relevant to digital images are performed, thereby causing recording in a recording medium. Then, the image data is compressed and encoded in a frame, thereby causing recording in a recording medium, while a time interval of intermittent recording exceeds a predetermined value. Thus even in the case where intermittent recording is performed over a very long time, an image quality is not degraded.
In addition, when the image data compressed and encoded in a frame, digital images of multiple channels are recorded in a memory in units of frames, thereby making it possible to see a desired site over a predetermined time in detail in the case where an attempt is made to strengthen monitoring midway.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.